The present invention relates, in general, to the field of magnetoresistive ("MR"), giant magnetoresistive ("GMR") and spin valve ("SV") type devices for use as magnetic "read" heads in computer mass storage devices such as disk and tape drives. More particularly, the present invention relates to a magnetoresistive sensor having a concave shape in the plane of the element in order to achieve a substantially single magnetic domain state and thereby reduce Barkhausen noise.
Magnetoresistive sensors are known to be useful in reading data from a magnetic surface with a sensitivity exceeding that of inductive or other thin film heads. In operation, an MR sensor is used to detect magnetic field signal changes as a function of the direction and amount of magnetic flux being sensed. It is also known that for an MR sensor to function effectively, it must be subjected to a transverse bias field to linearize its response. Various techniques for effectuating such transverse biasing are known, including current shunt, "barber pole" and soft adjacent film biasing. The transverse bias field is applied normal to the plane of the magnetic media and parallel to the surface of the MR sensor.
It is also known that an MR sensor may be utilized in conjunction with a longitudinal bias field extending parallel to the surface of the magnetic media and parallel to the major axis of the MR sensor. Stabilization of MR sensors by means of a longitudinal bias field is necessary for their application in high track density disk drives in order to suppress Barkhausen noise. Barkhausen noise results from unstable magnetic properties such as multi-domain states within the MR element which may appear, for example, following a magnetic disturbance from an associated write head or other external magnetic field source.
In this regard, magnetoresistive and spin valve magnetic recording "read" elements are commonly stabilized with antiferromagnetic ("AF") materials such as ferromanganese ("FeMn") or a permanent magnet ("PM") layer comprising cobalt platinum ("CoPt"), cobalt platinum tantalum ("CoPtTa") or cobalt platinum chromium ("CoPtCr") in order to pin the off-track boundaries and obtain a single magnetic domain state throughout the active MR element. However, the effectiveness of such boundary bias approaches diminishes in the center of the active region due to the fact that the flux rapidly leaks out of conventionally shaped (rectangular or convex) elements as the distance to the boundary increases. This undesired flux leakage results in multi-domain states with associated Barkhausen noise on read back and concomitant instability problems.